1. Field of the Invention
The present invention relates to a color image processing apparatus which digitally processes a color image.
2. Description of the Prior Art
Recently, the color image processing apparatus, such as a digital color copying machine and the like, has been demanded to perform the process for making the image as excellent as possible and to be equipped with a multifunctional performance.
A gradation correction performed in the conventional digital color copying machine, called a .gamma. correction, is used for correcting gradations of digital signals which are outputted from an image scanner for reading out an original and which are corresponding to three primary colors respectively (the magnitude of each of the digital signals is proportional to the light quantity of a corresponding primary color) to match the gradation characteristic of a printer (Japanese patent publication No. 59-161979).
Since the conventional digital color copying machine has the output gradation characteristic of the printer corrected directly by a conversion of color-separated signals from the image scanner, if a distortion of the output gradation characteristic of the printer becomes larger, the limited number of bits for quantizing the color-separated signals in the image reading unit results in a situation in which the distortion correction of the output gradation characteristic of the printer causes quantization steps to be more coarse. Thus, even if the color correction (MASKING) processing is performed, the exact color reproduction is impossible.
If the ground of the original copy is colored, the conventional digital color copying machine cannot reproduce the color of the ground to be white and the colors of an image other than the ground to be exactly as they are.
When setting the copying machine to a monochromatic copying mode, gray components are extracted from a plurality of color image signals, so that the image obtained by the monochromatic copying of the colored original becomes unnatural.